VUV photochemistry of oriented molecules: methylchloride on highly oriented pyrolytic graphite

Wilkes, John; Lamont, Christine L. A.; Šiller, Lidija; Coquel, J.M.; Palmer, Richard E.

doi:10.1016/s0039-6028(97)00558-x

Cited by 14 publications

(5 citation statements)

References 17 publications

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“…These features likely arise from the two known phases of CH 3 Cl on HOPG: one (β) in which the CH 3 Cl molecules lie with the C–Cl bond parallel to the surface and the other (α) in which the C–Cl bonds are almost upright. − Although it is known that the two phases exist in specific coverage ranges, their relative population is also temperature dependent, and the combined processes of heating and desorption in TPD mixes these effects when attempting to correlate desorption characteristics with phase identification. Similarly, the exposure temperature (105 K) is near a transition region in the CH 3 Cl/graphite phase diagram and is expected to influence the desorption feature growth .…”

Section: Resultsmentioning

confidence: 99%

Methyl Radical Reactivity on the Basal Plane of Graphite

et al. 2012

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The reaction of submonolayer Li atoms with CH 3 Cl at 100 K on a highly oriented pyrolytic graphite (HOPG) surface has been studied under ultrahigh vacuum. We exploit the low defect density of the high quality HOPG used here (∼10 9 defects cm −2 ) to eliminate the effects of step edges and defects on the graphite surface chemistry. Li causes C−Cl bond scission in CH 3 Cl, liberating CH 3 radicals below 130 K. Ordinarily, two CH 3 species would couple to form products such as C 2 H 6 , but in the presence of graphite, CH 3 preferentially adsorbs on the flat basal plane of Li-treated graphite. A C−CH 3 bond of 1.2 eV is formed, which is enhanced relative to CH 3 binding to clean graphite (0.52 eV) due to donation of electrons from Li into the graphite and back-donation from graphite to CH 3 . A low yield of C 1 , C 2 , and C 3 hydrocarbon products above 330 K is found along with a low yield of H 2 . The low yield of these products indicates that the majority of the CH 3 groups are irreversibly bound to the basal plane of graphite, and only a small fraction participate in the production of C 1 −C 3 volatile products or in extensive dehydrogenation. Spin-polarized density functional theory calculations indicate that CH 3 binds to the Li-treated surface with an activation energy of 0.3 eV to form a C−CH 3 adsorbed surface species with sp 3 hybridization of the graphite, and the methyl carbon atoms is involved in bond formation. Bound CH 3 radicals become mobile with 0.7 eV activation energy and can participate in combination reactions for the production of small yields of C 1 −C 3 hydrocarbon products. We show that alkyl radical attachment to the graphite surface is kinetically preferred over hydrocarbon product desorption.

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Section: Resultsmentioning

confidence: 99%

Methyl Radical Reactivity on the Basal Plane of Graphite

et al. 2012

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“…The Cl end collision reaches saturation coverage with smaller CH 3 Cl dose due to a higher occupation of the available sites via the dissociative adsorption, as compared to the CH 3 end collision. In the physisorption, weakly bound CH 3 Cl may be closely packed like on HOPG and the expected occupation of the available sites per incident CH 3 Cl molecule is smaller than in the dissociative adsorption. Thus, it is suggested that the molecular orientation dependence is caused by the route selection into the final destination of molecularly physisorption or dissociative adsorption during the trapping into the mobile precursor.…”

mentioning

confidence: 98%

Reaction-Path Selection with Molecular Orientation of CH₃Cl on Si{100}

2007

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We report direct evidence of steric effects in the dissociative adsorption of CH3Cl on Si{100} during the evolution of the coverage. The sticking probability (S) as a function of the amount of accumulated CH3Cl on the surface reveals the typical mobile precursor-mediated adsorption. For the Cl end collision, the decrease of S starts with a lower CH3Cl accumulation than for the CH3 end collision. Moreover, this steric effect depends on the surface temperature.

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“…In order to elucidate the role of the weak interaction potential, we performed scattering experiments for the CH3Cl/HOPG and Si(111) system. The CH3Cl/HOPG system is a weakly bound physisorption system, [98] while CH3Cl/Si(111) is a weakly bound physisorption/chemisorption system. [99] As we mentioned above, Bernstein et al also studied extensively the steric effects in the interaction between alkyl halide molecules and HOPG.…”

Section: Steric Effects In Ch3cl Scattering From Hopg and Si(111)mentioning

confidence: 99%

Supersonic Molecular Beam Experiments on Surface Chemical Reactions

Okada

2014

The Chemical Record

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The interaction of a molecule and a surface is important in various fields, and in particular in complex systems like biomaterials and their related chemistry. However, the detailed understanding of the elementary steps in the surface chemistry, for example, stereodynamics, is still insufficient even for simple model systems. In this Personal Account, I review our recent studies of chemical reactions on single-crystalline Cu and Si surfaces induced by hyperthermal oxygen molecular beams and by oriented molecular beams, respectively. Studies of oxide formation on Cu induced by hyperthermal molecular beams demonstrate a significant role of the translational energy of the incident molecules. The use of hyperthermal molecular beams enables us to open up new chemical reaction paths specific for the hyperthermal energy region, and to develop new methods for the fabrication of thin films. On the other hand, oriented molecular beams also demonstrate the possibility of understanding surface chemical reactions in detail by varying the orientation of the incident molecules. The steric effects found on Si surfaces hint at new ways of material fabrication on Si surfaces. Controlling the initial conditions of incoming molecules is a powerful tool for finely monitoring the elementary step of the surface chemical reactions and creating new materials on surfaces.

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VUV photochemistry of oriented molecules: methylchloride on highly oriented pyrolytic graphite

Cited by 14 publications

References 17 publications

Methyl Radical Reactivity on the Basal Plane of Graphite

Methyl Radical Reactivity on the Basal Plane of Graphite

Reaction-Path Selection with Molecular Orientation of CH₃Cl on Si{100}

Supersonic Molecular Beam Experiments on Surface Chemical Reactions

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VUV photochemistry of oriented molecules: methylchloride on highly oriented pyrolytic graphite

Cited by 14 publications

References 17 publications

Methyl Radical Reactivity on the Basal Plane of Graphite

Methyl Radical Reactivity on the Basal Plane of Graphite

Reaction-Path Selection with Molecular Orientation of CH3Cl on Si{100}

Supersonic Molecular Beam Experiments on Surface Chemical Reactions

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Product

Resources

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Reaction-Path Selection with Molecular Orientation of CH₃Cl on Si{100}